help plz.

You receive a $2,000 check from your grandparents for graduation. You decide to save it toward a down payment on a house. You invest it earning 8% per year and you think you will need to have $4,000 saved for the down payment. How long will it be before the $2,000 has grown to $4,000? To double the money you received from your grandparents, it will take years. (Round to one decimal place.)